m times the data interval will be added to each
end of that interval before it is used in autoscaling.
For example, if your data is in the range [0, 2], a factor of
m=0.1 will result in a range [-0.2, 2.2].

Negative values -0.5 < m < 0 will result in clipping of the data range.
I.e. for a data range [0, 2], a factor of m=-0.1 will result in
a range [0.2, 1.8].